# imgproxy integer overflow in ICO loader

Source: https://junglewise.ai/threats/imgproxy-has-integer-overflow-in-imgproxy-ico-loader-that-causes-denial-19f131eb  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

Severity: critical · CVSS 9.8 · Published 2026-10-30

imgproxy is an image processing service that converts and optimizes images on demand. An attacker who sends a specially crafted ICO image file can cause the service to crash (denial of service) or potentially execute arbitrary code on the server through heap memory corruption.

Technologies: [github.com/imgproxy/imgproxy (Go)](https://junglewise.ai/threats/technologies/github-com-imgproxy-imgproxy), [github.com/imgproxy/imgproxy/v2 (Go)](https://junglewise.ai/threats/technologies/github-com-imgproxy-imgproxy-v2), [github.com/imgproxy/imgproxy/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-imgproxy-imgproxy-v3), [Imgproxy](https://junglewise.ai/threats/technologies/imgproxy). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Imgproxy](https://junglewise.ai/threats/vendors/imgproxy).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Critical severity, with a CVSS score of 9.8, published 30 October 2026.

**Which products and versions are affected?** github.com/imgproxy/imgproxy (Go) >= 4.0.0, < 4.0.16, SEMVER:introduced=4.0.0,fixed=4.0.16; github.com/imgproxy/imgproxy/v2 (Go) >= 4.0.0, < 4.0.16, SEMVER:introduced=4.0.0,fixed=4.0.16; github.com/imgproxy/imgproxy/v3 (Go) >= 4.0.0, < 4.0.16, SEMVER:introduced=4.0.0,fixed=4.0.16.

**Is there a fix for This vulnerability?** Yes. github.com/imgproxy/imgproxy (Go): upgrade to 4.0.16 or later; github.com/imgproxy/imgproxy/v2 (Go): upgrade to 4.0.16 or later; github.com/imgproxy/imgproxy/v3 (Go): upgrade to 4.0.16 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network.

**Am I affected?** Check whether you run github.com/imgproxy/imgproxy (Go), github.com/imgproxy/imgproxy/v2 (Go), github.com/imgproxy/imgproxy/v3 (Go) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/imgproxy/imgproxy (Go): upgrade to 4.0.16 or later

  ```sh
  go get github.com/imgproxy/imgproxy@v4.0.16
  ```

- github.com/imgproxy/imgproxy/v2 (Go): upgrade to 4.0.16 or later

  ```sh
  go get github.com/imgproxy/imgproxy/v2@v4.0.16
  ```

- github.com/imgproxy/imgproxy/v3 (Go): upgrade to 4.0.16 or later

  ```sh
  go get github.com/imgproxy/imgproxy/v3@v4.0.16
  ```


## Technical details

An integer overflow in the ICO file loader (vips/icoload.c) occurs when the attacker-controlled 32-bit data_size field is added to BMP_FILE_HEADER_LEN (14 bytes) before memory allocation. For data_size values greater than UINT32_MAX - 14, the addition wraps, causing a tiny allocation. The vulnerable code then writes the attacker's declared data size into this undersized buffer, corrupting the process heap.

## Affected products

- imgproxy imgproxy

## Timeline

- 2026-10-30: disclosed

## Related threats

- [imgproxy integer overflow in ICO loader](https://junglewise.ai/threats/cve-2026-123614-imgproxy-from-4-0-0-before-4-0-16-contains-an-integer-overflow)
- [imgproxy unbounded memory allocation in ICO loader](https://junglewise.ai/threats/go-2026-6898-imgproxy-has-unbounded-memory-allocation-in-ico-loader-a99ea6ff)
- [imgproxy out-of-bounds heap read/write in ICO loader BMP header](https://junglewise.ai/threats/go-2026-6895-imgproxy-has-out-of-bounds-heap-read-write-in-ico-loader-d8e85817)
- [imgproxy integer overflow in ICO loader](https://junglewise.ai/threats/go-2026-6897-imgproxy-has-integer-overflow-in-imgproxy-ico-loader-that-dbf52154)
- [imgproxy out-of-bounds write in ICO loader BMP header](https://junglewise.ai/threats/imgproxy-has-out-of-bounds-heap-read-write-in-ico-loader-bmp-header-c4e077cd)